Analog-to-digital converters are commonly used in a wide variety of applications, including applications in a number of different types of wireless communication devices. Analog-to-digital converters are used to convert an analog signal into digital samples of the analog signal. In wireless communication, for example, analog waveforms may be received and processed in the analog domain, and then converted into the digital domain where information is demodulated. In the analog domain, for example, baseband signals are typically downconverted in frequency from carrier-modulated waveforms. The baseband signals may then be converted to digital samples, which can be demodulated in the digital domain. A variety of signal processing, such as filtering and scaling, is typically performed in both the analog an digital domains.
One type of analog-to-digital converter common in wireless communication applications, as well as other applications, is referred to as a sigma-delta (“ΣΔ”) analog-to-digital converter. ΣΔ analog-to-digital converters are particularly useful for wireless communication applications because they can shape quantization noise and push the quantization noise into frequencies that are outside of the frequencies specifically used for the wireless communication. This allows the converted digital samples to include a higher percentage of the signals of interest. A wide variety of other types of analog-to-digital converters also exist, and each respective analog-to-digital converter may be defined to output digital samples at one of several possible bit lengths.
One common problem with analog-to-digital converters is the possibility of saturation. In particular, each analog-to-digital converter has a dynamic range, and if signal power exceeds the dynamic range, the analog-to-digital converter will generate digital samples at the maximum of this dynamic range. If the analog signals exceed this maximum, the signals can be clipped and inaccurately represented by several successive maximum values by the analog-to-digital converter. When such saturation of the analog-to-digital converter occurs, information can be lost.
In wireless communication, saturation can sometimes occur due to “jammer” signals. Jammer signals refer to noise signals that do not correspond to the wireless signals supported by the respective wireless communication device. Jammer signals may be caused by signals sent from other devices operating according to protocols not supported by a device in question, signals emitted from microwave ovens, cordless telephones, other electromagnetic emitting devices, or the like. Jammer signals can be either constant or intermittent. In any case, jammer signals can sometimes cause saturation in the analog-to-digital converter and thereby undermine the ability to demodulate the signals of interest.